Glue applicator roll



Patented Jan. 4, 1944 GLUE APPLICATOR ROLL I Harry Galber, Seattle, Wash assignor to I. F.

Laucks, Inc., Seattle, Wash., a corporation of 1 Washington Application May 9, 1942, Serial No. 442,342

(cl; ill-67.8)

5 Claims.

This invention relates to improved grooved metal glue spreader rolls for spreading fluid\or semi-fluid glue on veneer core stock in the manufacture of plywood. The invention is directed towards securing greater precision in the deposit of the adhesive-in general and. also especially with a View to making the commercial use of low spreading rates more practical. Specific objects include elimination of troublesome'va'riations in the quantity deposited as between, wide and narrow pieces of core stock, obtaining better spreading of. rough veneer, and improving uniformity of deposit under varying conditions. Another important object is to make it possible to .obtain wide control of the amount of deposit by adjustment of the spreading pressure without need for changing or regrooving the rolls. Other objects and advantages will be apparent in the accompanying description.

For many years, plywood plants have. spread glue by passing the core stock through the bite of a pair of rolls, which, by means of their adjustment as'to tightness or pressure on the cores through and thus eliminate accumulation in the bite of the rolls which would interfere with uniform spreading. While this method of grooving glue spreader rolls has never been very satistaneously spread by the upper and lower rolls on both sides of the sheets of core stock veneer. This generous spread is needed both to secure the necessary long tolerance of assembly time i (or interval between glue spreading and pressing) and also to provide that, even in the case of poorly-cut, rough-surfaces veneer, the hollows and roughspots are all smeared with the glue in combination with the character of grooves cut on the roller surfaces, control the quantity.

and character of the deposit. These applicator rolls are usually made of steel pipe grooved spirally on a lathe to provide annular, or more exactly, spiral, alternating ridges and hollows similar to ordinary pipe threads. The crosssection of these grooves varies somewhat in detail but in general there are a seriesof ridges having a vertical height from the base of the groove to the top of the ridge running from about .032 inch to about .010 inch and a frequency or pitch from about sevento the inch to as much as twenty to the inch. These grooves are cut to give either a curved contour or else an area flat at the base with sloping sides which taper up'-' ward at an angle of between 45 and 70 degrees above horizontal. The top of the ridge provides the wood-gripping surface and is generally flat ing character of the individual plies.

and provided with a sufiicient amount to secure commercial adhesion notwithstanding the vary- Since the -cold process involves pressing stacks of panels even longer to build a whole stack, some of the en masse and it takes up to twenty minutes or "hot press process where assembly time is much or blunt. The general principle is to control the shorter and equally satisfactory adhesion can theoretically be\ obtained with only 45 to pounds of glue instead of to pounds. With rolls provided with more frequent and 'smaller grooves, this lower spread can be satisfactorily applied to smooth-cut core stock, but unfortunately results have not proved at all satisfactory if the core stock is rough or variable in thickness. A great many bare spots appear on the rougher areas and the narrower pieces' and those which are slightly thicker than the average do not receive enough glue. With the heavy spread and' relatively light spreading pressure of the cold process, these conditions have not been very serious, but with the lower hot press spreads, it has been necessary to decrease the size of the individual grooves, increase their frequency and also increase the spreading pressure. When the spreading pressure is increased for these low spreads, usin the small grooves, serious differences appear in the quantity spread on two successive pieces of core stock iione of the pieces is wide and the other narrow or ii a piece happens to be a little above normal thickness. This is due to the narrow piece receiving the same total pressure as the wide piece, and, since the same pressure is concentrated on a narrower area, the grooving indents itself deeper into the wood of the narrow piece and correspondingly reduces the deposit.

' ucts. With the cold process, it has been possible to make a considerable variation without changing the grooving of the rolls by merely adjusting the tightness with which the rolls grip the core stock, but when this is attempted with the lower spreads of the hot process it has been found that the range of control becomes much too narrow. Hence, while with the cold process one set of glue spreader rolls can meet a wide range of conditions, with the hot process either the cor-= rect spread cannot be obtained orican only be obtained by changing to a different pairof rolls grooved especially for that particular spread.

Another trouble is that some of the best new hot process glues are so expensive that their use essence tively fiat, shelf-like or step-section part way i down the sloping side of the ridge between the extremity and the root adapted to stop or limit the indenting action by increasing the woodcontacting surface and thus prevent the wood being pressed into the root or base portion of thegroove. Except for providing the cooperating features of a ridge having a wedge-like extremity and an intermediate, fiat, step-like area above the bottom of the groove, I prefer to follow the usual principles of cutting the grooves spirally like pipe threads and of adapting the volumetric total area of the groove to the desired quantitative range of glue spread.- I also preferably make use oi? the usualshallow, widely-spaced,

longitudinal or transverse grooves both to assist in discharging sawdust and accidental foreign material away from the bite of the spreader rolls the core stock.

and onto the surface of the plies which are being spread and also for the purpose of improving the uniformity of spread pattern deposited on I Attention is now drawn to the accompanying drawings in which:

Figure 1 is a diagrammatic side elevation of a typical pair of glue spread rolls. with the longisize and with the circumferential grooves shown is commercially impractical except with extreme- 1y uniform and low spreads. For example, some of the synthetic resin glues are capable of producing a very superior quality of plywood with spreads ranging between 45 and 60 pounds but their high cost makes it imperative that waste by excess deposit be avoided.

Thus far, only two solutions have been found and neither has proved very satisfactory. One solution has been to substitute grooved rubber rolls for the grooved steel rolls. This provides a flexible applicator able to conform in some degree to an irregular surface when using a low volume fine grooving and give a reasonably uniform, low spread provided the stock is fairly smooth. Even this method has failed with rough stock and it involves the serious disadvantage that the rubber rolls initially expensive and also diflicult to groove. The grooving soon wears on in-continuous service so that rubber rolls often have to be regrooved after three weeks use, while the grooving on "steel rolls will generally last from six months to a year and then is easily re-cut. The other expedient is to pass the core stock twice through fine-grooved steel rolls. This, of course, adds an objectionable extra operation although it generally produces a good spread.

After several years of experimental work, including extensive checking of results in commercial test operations in plywood plants, I have finally discovered that a. simple, inexpensive change in the cross-sectional contour, of theing steeply sloping sides adapted to indent the wood easily under the influence of the spreading pressure and then prdviding a. cooperating, reladiagrammatically;-

Figure 2 is an end elevation of Figure 1, with the longitudinal grooves similarly exaggerated; Figure 3 is an enlarged section of a common type of spiral grooving used in cold process practice, drawn on a scale of substantially fifty to one, based on dimensions given below;

Figure 4 is a similarly enlarged cross-section,

drawn on a similar scale, showing a type of spiral to the r the surfaces of a pair of rolls in accordance with the invention, and

Figure '7 is a fragmentary longitudinal section through a pair of such rolls and a veneer ply in operative position with respect theretd.

Referring to the drawings in detail: in Figure 1, numeral I indicates either of the-spreader rollers which are generally made froman 8 to 16 inch diameter shell of steel pipe strongly supported on journals 2 and provided with spirally-cut grooves 3 and longitudinal, shallow grooves or flutes 4.

The roller mountings always include means for adjusting the gap between the pair. of rollers to accommodate the thickness of the warmer and yielding means (usually adjustable springs) for regulating the pressure applied to the surface of the core stock. These devices are not shown since they are common to glue spreaders in general and is an intervening fiat, unexcavated area 5 which is usually called .a land" and provides a surface adapted to contact and grip the wood when it is fed through the bite of a pair of rollers. A common arrangement for this type of'grooving is to cut the groove 3 as an arc of a circle having a radius of .050 inch, the grooves being cut spirally at a frequency or pitch of ten to the inch with a vertical depth of the base of the groove below the level of the land of .020 inch. The extreme width of the outer portion of the groove will then be .080 inch.

Figure 4 is an enlarged cross-section of a similar spiral groove used mostly for hot process Work and difiering from the groove illustrated by Figure 3 merely in the feature that the curved contour is replaced b a flat base or root portion 6 with sloping sides 1 terminating in a flat-surfaced land 5. I

Figure shows an enlarged cross-section of the preferred form of groove 3' according to the present invention. It will be noted that it is very similar in contour to the form illustrated in Figure 4 except that, while a flat base 6' is provided with sloping sides I, an intermediate land, shelf or step-like area 8 is provided somewhatbelow the level of the outer land 5' and the sloping sides 9 above the shelf portion 8 are cut at a slightly steeper angle than. the surfaces ll, thus providing a relatively thin, wedge-like 'extremity or rib It] for gripping the wood while the shelf area 8 is capable of functioning as-a limit to the amount of wood indentation.

This operation is illustrated in Figure 7, where the wedge-like extremities II] are shown as indented into the wood veneer ply H, with'the step 'or shelf ,8 acting to limit the amount of wood penetration. The grooves 3' between the sloping groove side walls I are filled with adhesive I2 rate with a single set of rolls so that in order for a plant to meet operating conditions it is, ordinarily unnecessary to have more'than about two sets of rolls available. For example, in order to cover a range of spreads f rom about 50 pounds per thousand square feet to three-ply plywood up to about 150pounds', the grooves as provided to meet these extremes of range would be approximately as follows? I Spread 50 lbs. 150 lbs.

Total vertical depth of groove "finches 010 l 032' Vertical depth from land 5' to shell 8;. .do.-. 003 008 Vertical depth from shelf 8 to base 6'" "don 007 .024 Width of land 5 x... d0. .005 011 Angle above horizontal of sidewall 7 degrees. 52 52 Angle above horizontal of sidewall 9... ..do. .i 67. 5 67. 5 Greatest width of upper groove from land to land .t -ngchcz. 045 .100

t st width of lower roove mm 5 ep 0 ite pins...,L l f. ..inches.. .032 .072 Pitch or frequency of grooves per inch 20 9 Of course it is' understood that the above diin Figures 1, 2 and 6.

"topped ridges. were decidedly unsatisfactory because the per- We at mensions are approximate and illustrative and subject to such variations as usually occur in m1. chining metal to 'such small dimensions. How ever, in grooving rolls according to my invention, I prefer to use cold-drawn tubing which is adapted for smooth and accurate machining and I find it desirable to see that the Work is done as accurately as possible with carefully prepared cut-- ting tools on a good lathe and by a competent mechanic. Experience has shown that with these precautions there is no difiiculty in grooving rolls very closely to the desired dimensions.

In connection with the grooving of the preseni invention (for example, the form illustrated in. Figures 5, 6 and 7), I also prefer to use, as in. former practice, a series of lengthwise or horizontal, shallow grooves or flutes 3 as illustrated I prefer to space these grooves around the rolls at intervals of from /13. to 1 ,2 inches. Their section and dimensions are not critical. They may be channels with vertical walls and a flat base, but they are preferably of rather small area, for example, .010 inch deep by .020 inch wide. I find in practice that these horizontal flutes are of great value. because they not only assist, as previously described, in preventing the accumulation of sawdust in the bite of the spreader rolls but also, particularly with the more fluid glues, improve the linear charac ter of the pattern deposited by the spiral grooves by preventing the tendency of the lines originally deposited by the .individual grooves to coalesce from a fine linear pattern corresponding to the number of grooves and thus change to a coarse, irregular, smeary deposit. They also deposit a small amount of glue but their action as glue depositors is unimportant and merely incidental to their other functions.

, Practical experience in plywood mills has demonstrated a surprisingly wide range of advantages from the use of the present invention. While not limited to any particular field, it is especially successful in solving spreading difficulties in'the manufacture of fir plywood in general 'and its adoption removes the most serious obstacles to the extensive manufacture of fir plywood by hot press methods. I

In one typical instance, spreader rolls were in use for hot press glues. These rolls .had been grooved in the form illustrated by Figure 4 wherein the grooving takes the form of an excavatecl area bounded by simple, tapering, flat- With this grooving, operations miss ible spread variation with reasonably satis factory deposit was limited to a narrow range of between to 80 pounds of glue and within this range there occurred the usual troublesome "differences between the quantity-deposited on wide and narrow pieces of wood together with excessively low spreads on the occasional slightly thicker pieces of stock, frequent bare spots and poor distribution on rough stock. It was necessary for the spreader crew to discarda considerable number of. pieces due to unsatisfactory spread with consequenmwaste of veneer stock, glue and time.

. New rolls were substituted grooved according to the present invention 'as illustrated by Figures 5, 6, and 7 ariddesigned to have approximately the same volumetric groove area as the former rolls so asto permit spreading in the same range.

-It was now'found that the range of commercially satisfactory spreading (which, with the rolls out as per Figure 4, was limited between 65 and my principle of providing wed e-i came negligible as well as the amount of core stock discarded-after spreading due to failure to obtain satisfactory coverage. It was also found that, whereas former local variations in the quantity spread on different portions of some wide pieces of core stock had been troublesome, thi difiiculty disappeared. Improved ability to spread wavy or wrinkled core stock was also noted.

In another mill, where expensive synthetic A resin glues were being used for the production or extremely high grade plywood, it was found possible to replace rubber rollsby steel rolls groomed according to the present invention with entire satisfaction as to uniformity and control of spread and. with great reduction in maintenance costs due to the durability of the steel rolls as compared to that of rubber rolls.

Another advantage was found when certain types of casein blend glues were being used.

These are of a slippery character and trouble with former types of steel rolls had been encoun tered due to failure of the rolls to grip the veneer suiiiciently tightly to obtain positive feeding and avoid skidding or slipping of the veneer in its passage through the spreader. This slipping or skidding, or course, seriously interferes with obtaining a properly distributed, uniform deposit. It was found that the substitution of rolls grooved according to the present invention eliminated this trouble.

Successful spreading has also" been accomplished with the new type of rolls on glues oi a very wide range or viscosity including the semiflu'id glues described in United States Patent 2,1'28,5fi6 as well as with the fluid glues of ordi nary low viscosity. The invention is also suc cessful in spreading cold process glues in the lit usual heavy range of spreading rates as well as with the low spreading rates required by the newer hot process glues.

i'heuse of the invention is not confined to any single wood such as Douglas fir, but it is applicable to spreading plywood in general regardless of the species of wood, although its advantages have been found more important in handling soft woods where difierences between the hardness of the spring and summer wood forming the annual r'mgs are greatest and also when spreading species which are found difficult to cut smoothly on a veneer lathe.

The-advantages which have developed in the practical use of the present invention seem to exceed what might be expected. to result from extremities I9 adapted to indent or out easily to the gur face of the Wood M (Fig. '2) together with cooperating surfaces 8 adaut'ed to limit the extent of indentation. In retrospect after observing the results obtained, it appears probable that the wide range of spreading rate is due to the ease by which control or the pressure used in spreading the veneer ll controls the amount of indentation and consequent eflective groove area while the step'portion a of the groove acts to prevent excessive indentation occurring as a result-o1 excessive pressure due either to the naraccuses rowness of individual pieces 01' stock 5 i or to pieces being of slightly abnormal thickness.

It is seen that the former type or grooving does not provide these cooperating features since, if the outer extremities of the grooves are too blunt, control of spread by controlling the amount of indentation would be difllcult or impossible, while it they are too sharp or the indentation is excessive due to excessive pressure (as may occur on narrow or over-thick pieces of stock) then there is nothing to prevent the wood being pressed nearly to the bottom of the grooves which would naturally squeeze out most of the glue and result in an uncommercially 10w deposit.

It is also seen that with relatively sharp, thin ridges, it should be easier to obtain a spread in the cavities oi rought-cut stock, but it is not easy to explain the almost complete e imination of bare spots and other troubles mentioned in the foregoing description.

It is evident that the present invention may be applied in, various ways without departing from the principle of thin ridges adapted to indent the stock acting cooperatively with intermediate surfaces between the top of'the ridge and the base of the groove adapted to limit indentation.

I have found the method of applying these principles illustrated in Figure 5 to be preferable 3 from a practical standpoint, but it is readily seen that, instead of providing a shelf-area 8 on both sides of the ridge, substantially the same effect might be obtained by providing about the same area of shelf all located on one side of the ridge. In practice, however, I have found it easier cut the grooves accurately by providing shelf-areas on both sides of the ridge. lit also might be theoretically possible to obtain some of the benefits of the principles of this invention by cutting the grooves spirally with a double thread and forming one ridge with unbroken, steeply sloping sides terminating in a narrow land surface while the companion thread might have its whole top machined off to form a fiat surface at the lower level desired for the shelf or step shown in Figure 5.

It is also pointed out that, while the advantages of the invention are'commonly best obtained when using circumferential or spirallycut grooves, similar advantages may be obtained in some instances by providing longitudinal grooves of the same cross-section, this being of method of practicing the invention and is' not to be construed as limiting its application except as set forth in the appended claims.

I claim: v

'1. In a cylindrical metal glue spreader roll provided with a. grooved appllcatorsurface, the improvement which comprises providing the outer extremity of the ridge between adjacent grooves in the form of an outwardly projecting rib having steeply sloping sides adapted to indent core stock readily under normal spreading pressure and providing also, at an intermediate level between the extremity and root of the roove, a. relatively flat, shelf-Hike surface ptedto limit indentation.

2. In a cylindrical metal glue spreader roll provided with a spirally grooved applicator surface, the improvement which comprises providing the outer extremity of the ridge between adjacent grooves in the form of a rib having steeply sloping sides adapted to indent core stock readily under normal spreading pressure and providing also, at an intermediate level between the extremity and root of the groove, a relatively fiat, shelf-like surface adapted to limit indentation.

3. In a cylindrical metal glue spreader roll provided with a spirally grooved applicator surface having longitudinal grooves intersecting the spiral grooves, the improvement which comprises providing the outer extremity of the ridges between adjacent spiral grooves in the form of an outwardly projecting rib having steeply sloping sides adapted to indent core stock readily under normal spreading pressure and providing also,

at an intermediate level between the extremity 20 and root of the groove, a relatively flat, shelf-like surface adapted to limit indentation.

4. In a, grooved cylindrical metal glue spreader roll, the improvement which comprises in combination circumferential grooves including ridges between adjacent grooves, said ridges being shaped to provide outwardly projecting ribs having steeply sloping sides and relatively fiat, shelflike surfaces at an intermediate level between the extremity and root of the ridge, and longitudinal grooves spaced at relatively infrequent intervals and having steep side walls and a crosssectional area not exceeding the area of the circumferential grooves, whereby the step-form, circumferential ridges, by indenting the wood, tend to originally deposit the glue on veneer core stock in a series of corresponding ridges, and the horizontal grooves tend to prevent the glue ridges from coalescing to form, an irregular, smeary deposit.

5. In an annular or spirally grooved glue 25 the wood-contacting surface.

HARRY GALBER. 

